The present invention relates to an apparatus for securely clamping a transmission shaft of a transfer feed press during its shutdown.
As shown in FIG. 1, a conventional transfer feed press generally designated by 57 has slides 37 vertically movable through gearing and connecting rods 36 by a press drive which in turn is generally indicated by 1 and is disposed at an upper portion of the press 57. Part of the drive force from the drive 1 is transmitted through a transmission shaft 2 to a drive shaft 3 to swing bars 6 through a cam 4 and a link 5 carried by the shaft 3 so that a feed bar 7 is advanced in the direction indicated by arrow c and then returned in the direction indicated by arrow f, whereby a work 8 is transferred.
The shaft 3 has a cam 9 fitted over one end of the shaft 3 for reciprocation of an input shaft 11 on a bed through a mechanical interlocking mechanism 10 so that rotating force is transmitted to a plurality of shafts 14 through pairs of racks 12 and pinions 13 carried in a spaced-apart relationship by the shaft 11. The rotating force received by each of the shafts 14 is then transmitted through bevel gears 15 and 16 to a splined shaft 17 which is in engagement with a pinion 18. Then, the pinion 18 causes the feed bar 7 to move vertically through a lift rack 19 and a lift stand 20 so that the work 8 clamped by fingers 21 extending from the feed bars 7 is moved upwardly in the direction indicated by arrow b or downwardly in the direction indicated by arrow d.
A cam 22 is fitted over the other end of the drive shaft 3 to reciprocate an input shaft 24 on the bed through a mechanical interlocking mechanism 23 so that the rotating force is transmitted to a plurality of shafts 27 through pairs of racks 25 and pinions 26 carried by the shaft 24 in a spaced-apart relationship. The shaft 27 receives the rotating force and imparts thrust through a pinion 28 and a rack 29 to a rack shaft 30 which carries a rack 31, and transmits the thrust through the rack 31, a synchronizing pinion 32 and a rack 34 on a shaft 33. This results in moving the opposed feed bars 7 toward or away from each other laterally through feed bar supports 35 connected to the shafts 30 and 33 thereby carrying out the work clamping or releasing operation in the direction indicated by arrow a or e. In this case, the lift rack 19 is laterally displaced along with the pinion 18 since the latter is displaced along the shaft 17 in the axial direction thereof. Thus the feed bars 7 receive the power from the press drive 1 and accomplish the clamping operation in the direction indicated by arrow a, the upward movement in the direction indicated by arrow b, the feed operation in the direction indicated by arrow c, the downward movement in the direction indicated by arrow d, the releasing operation in the direction indicated by arrow e and the return movement in the direction indicated by arrow f.
Referring further to FIG. 1, the drive 1 includes a main motor 38, a main clutch 39 and a drive shaft 40 which rotates when the clutch 39 is engaged. As shown in FIG. 2, a main brake 41 with a ring gear 42 is securely attached to an end of the drive shaft 40. Upon replacement of a die, a micro-inching operation is carried out such that the main clutch 39 and a micro-inching brake 43 are released and then a micro-inching clutch 44 is engaged and a micro-inching motor 45 drives the drive shaft 40. Therefore, fine adjustment in height of the slide 37 can be accomplished through connecting rods 36.
In FIG. 1, reference numeral 46 denotes a motor with a clutch 47 and a brake 48 for adjusting the movement of the feed bars 7; 49, a brake for preventing the transmission shaft 2 from rotating when the drive 1 is de-energized, thereby securing the safety; 50 and 51, hydraulic cylinders adapted to detach the interlocking mechanisms 10 and 23 from the cams 9 and 22 upon maintenance or the like; 52, hydraulic cylinders for forcibly moving the feed bars 7 away from each other in case of emergency; 53, an air cylinder adapted to cause the interlocking mechanism 10 to press against the cam 9 upon the operation; 54, an air cylinder for biasing the opposed feed bars 7 toward the center of the line; 55, an overload coupling with a clutch; and 56, dies.
In addition to the above, there are various types of conventional transfer feed presses as disclosed in the Japanese Patent 1st Publication No. 23523/1983 and the Japanese Utility Model 1st Publication Nos. 2525/1988 and 25220/1988. Like the transfer feed press of the type described above, in any of the transfer feed presses disclosed in the above-described Publications, a drive causes feed bars to clamp a work, to move upwardly, to feed the work, to move downwardly, to release the work and to return. Works are sequentially fed while the slides are moved upwardly or downwardly, thereby pressing the work.
With the transfer feed press 57 described above with reference to FIG. 1, provided that any of the brakes 41, 43, 48 and 49 is broken, there is concern that upon the shutdown of the transfer feed press the slides 37 will move downwardly by their own weight and that their downward forces will be transmitted through the overload coupling 55 and the transmission shaft 2 to the feed bars 7, resulting in sudden movement of the feed bars 7.
Even if none of the brakes are broken, release of the pressures in the hydraulic cylinders 50, 51 and 52 or release of the pressing forces of the air cylinders 53 and 54 for maintenance may cause, depending upon the positions of the mechanisms 10 and 23, the gravity and other unexpected forced to be imparted to the drive shaft 3 and the input shafts 11 and 24. Thus, there is a fear that the drive shaft 3 will be forced to rotate and the input shafts 11 and 24 will be forced to move fowardly or backwardly, resulting in the movement of the feed bars 7 as described above.
Also in the transfer feed presses disclosed in the above-described Japanese Publications, release of the pressures in the hydraulic cylinders or release of the pressing force of the air cylinders may cause, under some conditions, feed bars to move due to the gravity and other forces imparted to the cam.
This is undesirable situation from a standpoint of safety since such sudden movement of the feed bars may lead to the injury of an operator or operators present in the installation for the purpose of maintenance or repair or replacement of a die during the shutdown.
In view of the above, it is a primary object of the present invention to prevent the sudden movement of the feed bars during the shutdown of the transfer feed press.